A magnetization method using a multi-pole magnetization yoke has been well-known as a method for magnetizing a multi-pole magnet of a magnetic rotary encoder.
FIG. 10 shows one embodiment of a conventional multi-pole magnetization yoke. A multi-pole magnetization yoke 110 magnetizes eight poles (N and S poles) on the circumferential face of an annular magnetic member 2. Eight magnetization projections 110a are circumferentially provided on a base part 110b. A coil for generating a magnetic field from each magnetization projection 110a is wound around the multi-pole magnetization yoke 110 (not shown in the figure). Electric current is supplied to the coil after positioning the magnetic member 2 relative to the multi-pole magnetization yoke 110, thereby the magnetic member 2 is simultaneously magnetized into eight poles.
In another magnetization method, the following Patent Literatures 1 and 2 disclose a rotary magnetization method in which the positive and the negative magnetic fields is alternately generated from a magnetization yoke for locally magnetizing an annular magnetic member, the magnetic member is rotationally moved relative to the magnetization yoke, and the N-poles and the S-poles are alternately formed on the magnetic member.